Modern disc drives are commonly used in a multitude of computer environments ranging from super computers through notebook computers to store large amounts of data in a form that can be made readily available to a user. Typically, a disc drive comprises one or more magnetic discs that are rotated by a spindle motor at a constant high speed. The surface of each disc is a data recording surface divided into a series of generally concentric data tracks, radially spaced across a band having an inner diameter and an outer diameter. Extending around the discs the data tracks store data within the radial extent of the tracks on the disc surfaces in the form of magnetic flux transitions, induced by an array of transducers or heads. Typically, each data track is divided into a number of data sectors that store fixed sized data blocks.
A read/write head includes an interactive element such as a magnetic transducer which senses the magnetic transitions on a selected data track to read the data stored on the track, or to transmit an electrical signal that induces magnetic transitions on the selected data track to write data to the track. The head includes a read/write gap that positions the active elements of the head at a position suitable for interaction with the magnetic transitions on the data tracks of a disc as the disc rotates.
As is known in the art, each head is mounted to a rotary actuator arm and is selectively positionable by the actuator arm over a pre-selected data track of the disc to either read data from or write data to the pre-selected data track. The head includes a slider assembly having an air bearing surface that causes the head to fly over the data tracks of the disc surface due to air currents caused by rotation of the disc.
Typically, multiple center open discs and spacer rings are alternately stacked on a spindle motor's hub. The hub, defining the core of the stack, serves to align the discs and spacer rings around a common centerline. Collectively the discs, spacer rings and spindle motor hub define a disc stack envelope. The surfaces of the stacked discs, forming a disc stack, are accessed by the heads mounted on a complementary stack of actuator arms which compose an actuator assembly, or "E-block". The E-block generally includes head wires which conduct electrical signals from the heads to a flex circuit, which in turn conducts the electrical signals to a flex circuit bracket mounted to a disc drive basedeck. For a general discussion of E-block assembly techniques, see U.S. Pat. No. 5,404,636 entitled METHOD OF ASSEMBLING A DISC DRIVE ACTUATOR, issued Apr. 11, 1995 to Stefansky et al., assigned to the assignee of the present invention.
A continuing trend in the industry is the reduction in size of modern disc drives. As a result, the discs in the disc stacks of modern disc drives are increasingly being brought closer together, providing narrower vertical gaps between adjacent discs. Although facilitating greater amounts of storage capacity, such narrow vertical spacing of the discs gives rise to a problem of increased sensitivity of the disc drives to non-operating mechanical shocks; particularly, predominant failure modes in modern disc drives have been found to include damage to the surfaces of the discs, damage to the sliders and load arms, and damage to the actuator arms as a result of contact between the actuator arms and the discs from mechanical shocks encountered during the shipping and handling of the drives. Computer modeling has shown that the first mechanical bending mode of the discs typically causes over fifty percent of the motion between the arms and discs in selected disc drive designs. The bending mode is generally dependent upon the material, diameter and thickness of the discs, and these factors are not readily modified in a disc drive design.
Additionally, as disc drives continue to decrease in size, smaller heads, thinner substraights, longer and thinner actuator arms, and thinner gimbal assemblies will continue to be incorporated into the drives, significantly increasing the need to protect the disc drives from damage as a result of incidental contact between actuator arm/gimbal assemblies and the surfaces of the discs.
Coupled with increased mechanical performance demands, imposed by designed size reductions of disc drives, are market requirements that demand ever increasing non-operating shock performance. In response to these demands alternative solutions have begun to emerge. Some sub drives with disc diameters of less than 95.0 millimeters (3.74 inches, commonly referred to as a standard "3.5 inch form factor") have met the demand through the use of ramp loading technology. The improved performance is obtained by eliminating head induced media damage through the removal of the heads from the discs. Ramp loading technology implementation is less demanding in sub 3.5 inch form factors, especially those with fewer discs. In designs using fewer discs of smaller diameter the ramp loading apparatus need not protrude over the disc surface or intrude into the space between the discs. However, an increase in disc diameter necessitates the need for the ramp loading apparatus to protrude over the disc surface or intrude into the space between the discs, as the load point remains inboard the disc outer diameter. Increasing the number of discs in the disc stack heightens the demands of maintaining the dimensional, mechanical and operational integrity of the ramp loading apparatus.
Attempts to extend the ramp material over the discs, while assuring non-interference with outer diameter read/write functions, necessitate a substantial reduction in the thickness of the ramps. Reductions in thickness sufficient to insure non-obstruction of drive function result in insufficient strength and rigidity in the ramps to withstand the forces encountered during the loading operation.
There is a need for an improved ramp loading apparatus for complex disc drives to reduce the susceptibility of damage to those disc drives as a result of non-operating mechanical shocks.